The Effect of Municipal Landfill Leachate on the Characterization of Fluid Flow through Clay

Federal and state regulations prescribe design requirements for low permeability clay landfill liners based on saturated hydraulic conductivity. The assumption that clay liners are saturated for the duration of their life is a simplification of the true processes at work. The fact that clay liners are compacted to optimum, or just wet of optimum, proves that they are initially subject to unsaturated conditions, and it is well known that liners can remain variably saturated for the duration of their life. While this is appropriate for landfill cover liners, leaching affects may drastically change pore fluid chemistry as water moves through the landfill to the bottom liner. In this study the goal is to determine the affect of modeling two different pore fluids—leachate and water. This research uses an approach that critically assesses how leachate will move through a landfill bottom liner differently than water. The result of this study is the affect of leachate on the soil-water characteristic curve and a quantitative comparison of how a liner would be expected to perform when permeated with leachate versus water. Samples prepared with leachate resulted in lower water content than samples prepared with water. Both the Van Genuchten and Cory-Brook models fit the data (leachate and water) very well. At higher (400 cm of water) the difference between the leachate samples and water sample became obvious.